The correspondence series includes a large quantity of letters written from August Belmont VI to Margaret Hayden Rector. The letters address the history of the Belmont family, horse racing, construction of the Cape Cod Canal, philanthropic work, health concerns, the Belcourt house, New England winters, summer gardens, employment experiences, literature, and family relationships. Along with the letters in this series there are a number of academic articles written on the Belmont family.